DOC* Algorithm: Docking Orientation Constrained Path Planning for Robust Autonomous Docking

Autonomous docking is a crucial technology for unmanned surface vehicles (USVs). Due to the inherent challenges of lateral control in ships, it is essential to account for their kinematic constraints when generating safe docking paths without relying on auxiliary systems such as lateral thrusters or external assistance from other vessels. In particular, rapid orientation changes near docking facilities can lead to collisions. Therefore, minimizing the difference between the ship’s current orientation and the docking orientation prior to approach is critical for safety. To address these challenges, we propose a novel cost function integrated into a 3D A* path planning algorithm. The algorithm operates in two stages: 1) graph generation, which constrains the orientation transitions based on the ship’s maneuverability; and 2) node search, which employs a cost function that jointly minimizes lateral distance and orientation deviation. The effectiveness of the proposed method is demonstrated through case studies and simulations under various docking scenarios, and its feasibility is validated through real-world experiments conducted with an actual ship, where the results are compared against other path planning algorithms.